The quality or state of being grewsome; the degree to which something is disturbing or horrifying.
Formed from 'grewsome' plus the noun-forming suffix '-ness,' a common English pattern for creating abstract nouns. The suffix '-ness' transforms adjectives into nouns describing their inherent quality.
English's '-ness' suffix is a word-building machine: add it to almost any adjective and you get a valid noun, which is why non-native speakers can sometimes create words that sound odd but are technically grammatically perfect.
Complete word intelligence in one call. Free tier — 50 lookups/day.